This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. In the rhodopsin family of G-Protein Coupled Receptors (GPCRs), absorption of light and isomerization of the retinal chromophore from the 11-cis (inverse agonist) to the all-trans (agonist) geometry triggers a sequence of protein conformational changes ultimately leading to the formation of the pre-activated Meta-1 state on the microsecond timescale, followed by the activated Meta-2 state on the millisecond timescale. To begin to understand the conformational changes that characterize the activation of the squid rhodopsin GPCR, we propose microsecond timescale molecular dynamics (MD) simulations of squid rhodopsin in a hydrated lipid bilayer consisting of 1-stearoyl-2-docosahexaenoyl- sn-glycero-3-phosphocholine (SDPC) lipid molecules.